This science project requires a Squishy Circuits Kit and ingredients to make conductive and insulating play dough. See the Materials and Equipment list for details.

Cost

Low ($20 - $50)

Safety

Ask for an adult's help when using the stove to make the conductive play dough. Never connect the battery pack's terminals directly to each other; this is called a short circuit and can make the batteries and wires get very hot. Do not connect the LEDs directly to the battery pack without using play dough; this will burn out the LEDs.

Abstract

Do you enjoy sculpting animals and other three-dimensional creations with play dough and modeling clay? Imagine adding lights to a house you've built, or glowing eyes on a dinosaur you've created. There are countless possibilities! In this science project, you will make play dough that conducts electricity so you can add lights to your three-dimensional creations.

This science project is the third in a three-part series on squishy circuits, which can all be done with the same materials. We recommend doing the science projects in order.

Objective

Make conductive and insulating play dough, and use them to create a three-dimensional sculpture that lights up.

Credits

Ben Finio, PhD, Science Buddies

This project idea is based on the Squishy Circuits project originally developed at St. Thomas University.

In this science project, there is no new information to learn about circuits. Instead, you will apply what you have already learned to light up a three-dimensional structure. This is what engineers do; they apply scientific concepts to build interesting, fun, or useful products. A couple of important reminders before you get started: Remember that you need to attach your LEDs in parallel so they will all light up brightly, and you need to use layers of insulating dough to prevent short circuits. But beyond that, there are no rules; your imagination is the limit!

To help you get started, check out the "frog" example:

Figure 1.
Example of a three-dimensional squishy circuit creation: a frog with LEDs for eyes.

The secret to lighting up the frog's eyes without creating a short circuit is to use a layer of insulating play dough to separate the frog's back from its belly and feet. This is shown in Figure 2.

Figure 2.
The frog is made out of two separate pieces of conductive play dough: one for its back and one for its belly and feet. These are stuck together with a layer of insulating play dough. Each LED then has one end plugged in to the top layer, and one end plugged in to the bottom layer. This creates a parallel circuit, and the eyes light up!

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Materials and Equipment

Note: if you have already purchased a Squishy Circuits Kit and the materials to make conductive and insulating play dough for a previous squishy circuits science project, you can reuse those materials and do not need to buy new supplies..

Order Product Supplies

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Experimental Procedure

Note: This engineering project is best described by the engineering design
process, as opposed to the scientific method. You might want to ask
your teacher whether it's acceptable to follow the engineering design process for
your project before you begin. You can learn more about the engineering design process
in the Science Buddies
Engineering Design Process Guide.

Making the Electric Play Dough

Follow the directions in your Squishy Circuits Kit to make conductive and insulating play dough. The directions are written on the inside of the lid of your Squishy Circuits Kit, and we have reproduced them here for convenience. You can also watch videos, below, of how the conductive and insulating play doughs are made. Important: Ask an adult to help you use the stove to make the play doughs.

Stir the mixture from step 1 continuously over medium heat until a dough ball forms.

3

½ C. flour

Turn off the stove. Carefully remove the pot from the heat and dump the play dough back into your mixing bowl.

Wait several minutes for the mixture to cool. Once it has cooled down, knead (mix the dough with your hands) in additional flour until desired consistency is formed.

Table 1. Directions for making conductive play dough.

This video
is a step-by-step tutorial on making the conductive play dough. It should help answer any questions you have about how to judge the consistency of your play dough at each step.

Insulating Play Dough

Important: We found that adding the full ½ C. of distilled water to the insulating dough in step 2 was too much (the dough became too sticky). Be sure to add small amounts of water slowly as you stir, and stop when the dough has reached a good consistency.

Step

Ingredients

Procedure

1

1 C. flour
½ C. sugar
3 tbsp. vegetable oil

Mix all the ingredients in a clean mixing bowl (especially if you used food coloring to make your conductive play dough).

Note that you are only including 1 C. of flour for now.

2

½ C. deionized or distilled water

Slowly add small amounts of water as you continuously knead the dough.

Do not add the whole 1/2 C. of water at once or your play dough may become too sticky. You might not need to use the whole ½ C.

3

½ C. flour

After a dough ball has formed, knead in additional flour to remove stickiness.

Table 2. Directions for making insulating play dough.

This video
is a step-by-step tutorial on making the insulating play dough. It should help answer any questions you have about how to judge the consistency of your play dough at each step.

Engineering Your Light-Up Sculpture

Insert the four AA batteries into the battery pack that came with your kit.

Now, plan out the three-dimensional creation that you want to make and how you want to add lights. It might help if you sketch your design on paper. Remember that you need to connect your LEDs in parallel, and that the actual shape of the play dough does not matter, as long as each LED has its own "loop" formed with the battery. You might need to use insulating play dough in some places to prevent a short circuit. Once you have a plan, start building!

If your LEDs do not light up, remember to try reversing them, because electricity can only flow through them in one direction. Also make sure your battery pack is turned on. If you are having trouble, consult the
FAQ
for other tips and tricks.

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Variations

Your Squishy Circuits Kit also came with a motor and two buzzers. Can you add those to your creation somehow?

Curious about the chemistry behind electric play dough? Research what ingredient or ingredients make the play doughs conductive or insulating; then try changing the recipes to see what it does to the conductive and insulating properties of the play dough. For instance, how much salt do you need for the play dough to conduct electricity?

A: If your play dough is too wet and sticky, you can slowly knead in extra flour to dry it out. If your play dough is too dry and crumbly, you can slowly knead in extra water.

If you are making a new batch of dough, the best way to prevent these problems is to follow the directions carefully and measure the appropriate amount of each ingredient. Some steps require you to slowly add small amounts of water until the desired consistency is formed, instead of adding the entire amount all at once.

Q: I'm not sure if my Squishy Circuits Kit is working.

A:

Make sure you properly inserted the batteries into the battery pack. Each battery is marked with a "+" symbol on one end. Make sure these symbols line up with the "+" symbols on the inside of the battery pack.

Make sure you turn the switch on your battery pack to the "on" position when you are testing your circuit.

As a simple test, try connecting the motor leads directly to the battery pack leads using lumps of conductive play dough. The motor should spin regardless of which way you connect the leads.

Make sure your conductive play dough is tightly secured around the metal leads for your battery pack and motor. If you wiggle them around a lot and they come loose, then they will not be in good contact, and it will be difficult for electricity to flow.

If you have a multimeter, you can use it to measure the voltage from your battery pack. Four AA batteries should provide about 6 volts (V). If the voltage is lower than 6 V, your batteries might be dead. Consult the
Science Buddies Multimeter Tutorial if you need help using a multimeter.

If your motor still does not spin after trying all the steps above, try putting new batteries in the battery pack.

Q: My LEDs won't light up.

A:

Remember that LEDs have a polarity, meaning they only work in one direction.
The longer LED lead should be connected toward the positive side of your circuit, which is the side with the red wire protruding from the battery pack. If one LED in your circuit is not lighting up, but others are, you probably just have that LED plugged in backwards. Try reversing its direction and see if it lights up.

Make sure your conductive play dough is tightly secured around the metal leads for your battery pack and motor. If you wiggle them around a lot and they come loose, then they will not be in good contact, and it will be difficult for electricity to flow.

Make sure you do not have a short circuit. For more information about short circuits (including pictures and diagrams), refer to the Introduction of the first Electric Play Dough project.

If your circuit has two or more LEDs, make sure they are wired in parallel and not in series. Wiring multiple LEDs in series will quickly cause them to become very dim. For more information about the difference between series and parallel circuits (including pictures and diagrams), refer to the Introduction of the second Electric Play Dough project.

Make sure you are not using very long pieces of conductive play dough to connect your battery terminals to your LEDs. The conductive play dough has a fairly high resistance, which causes the voltage to drop as electricity travels through it. If you use very long pieces of conductive dough, the voltage might drop so much that the LEDs will not light up. To learn more about voltage and resistance, check out the
Science Buddies Electronics Primer Introduction.

Never connect your LEDs directly to the battery pack leads without using conductive play dough in between. Connecting LEDs directly to the battery pack will cause them to burn out; too much current will flow, permanently destroying the LED. If you have LEDs that do not light up at all despite trying all the steps above, you might have accidentally burned them out at some point.

Q: Some parts of my circuit work and some don't.

A:

In general, follow the same steps as in FAQ 3. For a big circuit, it is possible to have a short circuit in only part of the circuit; some LEDs might light up, while others stay dark. You might have also accidentally wired some LEDs in series, and some in parallel. Remember to always avoid short circuits, check the direction your LEDs are plugged in, and make sure your LEDs are wired in parallel.

You can test individual parts of your circuit, one at a time. You can do this by breaking them away from the rest of your circuit and connecting them to the battery pack separately, or by sticking the battery pack leads into different parts of your circuit. This will let you identify problem areas in your circuit.

Remember that it is possible to burn out LEDs by connecting them directly to the battery pack. If nothing else works, try swapping in a new LED.

Q: How should I store my play dough? How long will it last?

A:

Both types of play dough (conductive and insulating) should be stored in air-tight plastic containers or plastic bags.

The conductive play dough contains salt, so will last for several weeks or months if kept in an air-tight container. Eventually, you may still see spots of mold or bacteria growing on it.

Insulating play dough contains sugar, which bacteria and other microorganisms thrive on. You may start to see mold or bacteria growing on it after several days or a week.

If your play dough develops spots of visible mold or bacteria, you should throw it away and make a new batch.

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Contact Us

If you have purchased a kit for this project from Science Buddies, we are pleased to answer any question not addressed by the FAQ above.

In your email, please follow these instructions:

What is your Science Buddies kit order number?

Please describe how you need help as thoroughly as possible:

Examples

Good QuestionI'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?Good QuestionI'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.Bad QuestionI don't understand the instructions. Help!Good QuestionI am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?Bad QuestionCan I use a different part?

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